We rely on discharge data to inform us about water availability.

This reliance is based on an assumption that discharge data represents information both about the hydrology upstream of the gauge as well as hydraulic conditions downstream of the gauge. Zero flow marks the point of departure between this assumption and the truth. Now I would like to further expand on this theme that our ‘measurements of nothing’ really matter.

Several years ago I walked extensive sections of the Little Campbell River at low water as part of a study investigating links between land-use and water quality. I discovered long sections of dry river bed, even though flowing water was observed both further upstream as well as downstream.

It is not unusual for land-use change to result in soil loss with resultant sediment deposition in the stream. These slugs of sediment are pushed downstream through successive storm events. The stream bed is raised in the deposition zone, a process called aggradation.

In this case, reach scale aggradation was likely due to active landscape transition from rural to suburban development. During low water events the river volume can be insufficient to breach the aggraded river reach, but the upstream water pressure can be sufficient to force the water into the hyporheic zone, from which it eventually emerges downstream of the aggraded reach. The aggraded reach can, in this way, become dewatered during the low flow season.

Consider the analysis of a time series of data for a stream with a change in land use.

A pulse of sediment may progress through the gauging section over the span of several years. There may be zero flow at the gauge during low flow periods while the flow might be perfectly ‘normal’ both upstream and downstream. A naïve analyst may be alarmed at the unprecedented occurrence of zero flow in the data and incorrectly attribute the effect to an unrelated cause (e.g. to climate change).

Another interesting project was an investigation of a regional statistical model for the estimation of the annual low flow by validation against local scale data. For this experiment we conducted a longitudinal study of discharge on the Koidern River in South West Yukon during the late winter. The results were really interesting because the data plotted almost orthogonally to the predictive relation.

The reason for this was a massive buildup of ice at each confluence of the river resulting in series of ice dams. Each dam would force more water into the hyporheic zone resulting in a net dewatering of the river in a downstream direction.

The most fascinating observations of this study were of the linkage between the hydrology of zero flow and ecology.

At each ice dam water would be forced into the hyporheic zone to emerge in a downstream pool formed behind the next ice dam. These pools were ‘nearly’ ideal winter refugia for fish. I say ‘nearly’ ideal because these refugia were not as perfect for the fish as for a family of fat river otters I enjoyed watching as they played in the snow. I presume these otters appreciated having an abundant supply of captive fish for their dining pleasure.

Even more interesting is the Fishing Branch River in the Northern Yukon. Unfortunately, I was never able to secure funding for an investigation of this river. It has been noticed in recent years that a section of river has been going dry in late August and September. This is important because the dry channel is a barrier to the run of Chum Salmon. Salmon returns are now in the range of about 30,000 fish, whereas in the early 1970’s runs in excess of 300,000 were observed.

The Fishing Branch is ideal for spawning because of a very unusual hydrological phenomenon.

It always has ample flow through the winter season. This flow must be from a deep groundwater source because there is no apparent source of runoff during the long Yukon winter and the source is warm enough that the river stays open even during extended periods of extreme cold (< -40 oC!) temperatures. The question that remains unanswered is: why would the river (increasingly) go dry in late summer but then have plenty of water during the long Yukon winter?

Even measurements of small flow require special attention. For example, late winter measurements at Big Creek in the Yukon were challenging. There would only be a very small amount of flow under 1.5 to 2.0 m of ice covering the channel at the gauge. It was necessary to drill to bed to locate the flowing channel under a very large volume of ice, taking a lot of time and ruining many ice drill bits. Conveniently, there was a section of river a short distance downstream that stayed open year round providing a location for an easy winter wading measurement saving us considerable time and effort. It took several years for us to notice that late winter flow was always substantially higher at this wading section than at the gauge in spite of no apparent source of inflow.

Understanding and accurately characterizing water availability has arguably never been more important than it is now. This is likely to become even more critical in coming years as a result of changing climate and land use. The study of ephemeral streams is needed to develop our ability to manage water wisely.

However, in order for measurements of zero flow to benefit our understanding of water availability, we need to provide sufficient context for this most important number.

Is there flowing water anywhere upstream of the gauge? Is there water flowing downstream of the gauge? Is there standing water anywhere in the channel with zero velocity? Are there fish taking refuge in these pools or disconnected river reaches? Has there been a change in the offset of the rating equation? This last question is important for attribution of cause. In any case, notes, maps, sketches, and photographs of zero flow may be as important as the data itself. Every aspect of small and zero flow gauging can be very important for accurate interpretation of the data.

How important are intermittent streams?

Acuna et al. (2014) report that flow intermittency is so common that it makes up the majority of river networks in many regions. One third of fifth-order rivers and almost 70% of first-order streams south of 60o latitude only flow intermittently. Temporary waterways perform complex and vitally important ecosystem services. Temporary waterways are under increased stress because they are not always managed with the same care as permanent waterways. In the EU a temporary stream or river may not be considered a water body, whereas Australian state and federal legislation explicitly include temporary streams and rivers. Policies will continue to evolve and be informed by new science on the role that intermittency plays in water quality and quantity. This science must, in turn, be informed by accurate measurements and monitoring of absolutely nothing.

4 responses to “The Other Extreme – Part 2: ‘Nothing’ Matters”

Thank you Stu for this “The Other Extreme” series of yours, very much appreciated.
Here in Cyprus we are monitoring temporary rivers since the 1950s, covering all the regime gradient from intermittent to ephemeral/episodic, and it is this very data that allowed me to produce a refined mapping of temporary rivers and related typology – this being the typology to be used for WFD implementation (cf. the Acuna et al. 2014 paper) in our country from now on. In that sense, I can only agree that the first step to improved management of temporary rivers is to understand their flow regime.
So we will keep taking our notes on zero flows – whether this be true zero or just “zero on the weir sill”. And apart from having an idea at a point in time, which of the two is just happening, it is also crucial to have an appreciation of the interannual longitudinal shifts of regime along the river, in the sense of the fuzzy zones described by Uys & O’Keeffe 1997.
Concluding, I am very happy to see you picked up that topic, and am looking forward to the next “chapters”.
best,
Gerald

Thanks for pointing out the Uys and O’Keeffe, 1997 article. Arguably, my sense of humour needs calibration but I find it a bit ironic that the intent of the paper is to address the confusion arising when terms such as “dryland”, “temporary”, “seasonal”, “intermittent” and “ephemeral” are used inter-changeably and then they use the term “Temporary River” in their title. Clearly, a descriptive terminology system such as they propose would address the problem but the risk is that anyone working in “dryland”, “temporary”, “seasonal”, “intermittent” and “ephemeral” streams may not discover their work for the very reason of a lack of agreement on terminology.

Keep up the good work in Cypress. I can well imagine how important an understanding of “temporary” flow is for managing your precious water resources.

Stu: This article on zero flow is interesting but confusing from the practical point of view. We either have flow or do not, there is no in between. Ephermeral streams have flow at certain periods, and the rest of the time their flow is zero. Your portrait of this process is too complex for the average streamgager.

My intention is not to confuse but to ask provocative questions. Zero as a number (http://en.wikipedia.org/wiki/0_(number)) is a relatively new to mathematics, arguments against the need for a number zero are based on the question “how can nothing be something?”. Seeing as it has confused the best and brightest scholars, philosophers and mathematicians for millennia, being confused by zero puts us in very illustrious company.

My hope is that hydrographers will pay close attention when observing zero flow and collect and document sufficient ‘soft’ data to enable water managers to better manage and researchers to do better research with this critically important extreme measurement of discharge.

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Water News

This blog post is a fantastic insight into the minds of the most influential hydrologists in the world today. The question: “WHAT BOOK OR PAPER HAS BEEN MOST INFLUENTIAL TO YOUR CAREER AND WHY?” was posed to senior hydrologists all over the world and the answers run from the predictable (Groundwater by Freeze and Cherry), the unexpected (House at Pooh Corner), classic (The Method of Multiple Working Hypotheses), eclectic (Slowness) to difficult (Scale of Fluctuation of Rainfall Models). Out of this broad range of influential reading, it is the explanation of why a particular body of work made a difference in a career path that is most illuminating. I particularly like the quote provided by Gregory Pastenack: “Show me a person who has read a thousand books and I’ll show you my best friend; show me a person who has read but one and I will show you my worst enemy.” Happy reading. – Stu Hamilton

The intent of this paper is to develop a system of diverse observation systems for the purpose of ground-truthing satellite observation systems. The challenge is that while it is possible to develop methods to identify incorrect data, the residue is not necessarily all correct data. Confidence in the data has to come from attributes such as whether the data source is well documented, well understood, representative, updated, publicly available, and maintains rich metadata. If broadly adopted, the system-of-systems approach will have potential benefits in guiding users to the most appropriate set of observations for their needs and in highlighting to network owners and operators areas for potential improvement. – Stu Hamilton

Murky Waters: Taking a Snapshot of Freshwater Sustainability in BC

This statement: “There’s a huge opportunity here to improve data collection, monitoring, and reporting. Reliable data would help governments, funders, and non-profits to track progress, make better decisions, and coordinate their efforts” is from Jack Wong, the CEO of the Real Estate Foundation of BC. The recommendations of this study include: “Regular public opinion surveys on freshwater attitudes (…) conducted by a cross-section of water partners to ensure long-term availability of the data”; “A multi-faceted solution (…) involving diverse groups that gather water data to increase the quantity and quality of data and improve data accessibility”; “This report shows a huge opportunity to convene relevant players and discuss solutions for freshwater sustainability data collection, monitoring, and reporting. If successfully implemented, communities across the province will be more informed and better stewards of BC’s most precious resource.” – Stu Hamilton

Attribution of cause to effect in natural environments is a difficult problem. It is one thing to be able to use monitoring data to say what is happening. It is much more challenging to say why it is happening. While difficult, attribution is important. Without compelling attribution, there are deeply entrenched reasons to stay the course and not make the changes necessary to achieve better outcomes. I am interested to know if the relatively simple method used in this paper for attribution of cause to extreme temperatures could be applied for other types of data. For example, wouldn’t it be good to have compelling attribution of cause for harmful algal blooms? – Stu Hamilton

This report makes a compelling argument about how looking after water is in the best strategic interests of the United States. It is better to anticipate predictable problems and take relatively inexpensive actions (e.g. wise use of data to influence proactive measures) to avoid or mitigate challenges to human health and economic development, both of which must be managed to ensure peace and security. – Stu Hamilton

Print this article and put it on the desk of the senior administrators in your water monitoring agency. The arguments made here that climate observation networks offer a magnified return on investment all hold true for water monitoring as well. “Climate change is but one example of the need to make decisions under deep uncertainty. Developing new approaches to decision making that go beyond traditional point and probabilistic predictions is the focus of a new scientific undertaking. Developing adaptation pathways that will be robust under many possible futures will in part require observing systems that are designed with these needs in mind.” “The economic value of such a system at ~ $10 trillion dollars to the world economy in today’s value (known as “net present value” in economics using a 3% discount rate). In the simplest sense, this is the economic value of moving climate scientific understanding forward 15 to 20 years by using better observations, analysis, and modeling capabilities. The studies further estimated that if the world tripled its current economic investments in climate research (observations, analysis, modeling) to achieve such an advanced observing system, the return on investment would be ~ $50 for every $1 invested by society.”

The average global temperature from January to September 2017 was approximately 1.1°C above the pre-industrial era. The years of 2013-2017 are set to be the warmest five-year period on record. The past three years have all been in the top three years in terms of temperature records. The WMO statement is based on five independently maintained global temperature data sets. The rate of increase in CO2 from 2015 to 2016 was the highest on record, 3.3 parts per million/year, reaching 403.3 parts per million. – Stu Hamilton

This paper affirms the central theme of my whitepaper “Improving Outcomes for Freshwater Availability, Security and Sustainability: Water Data Asset Management as a Strategic Investment.” The key to good governance is well-informed stakeholders. Water monitoring best serves public interests when data is managed as a strategic asset. – Stu Hamilton

I like this blog post for how it explains catchment processes as a lead-in to explaining the value of isotope hydrology. I think this approach is a good one for anyone in monitoring to remember when explaining what we do and why we do it. Start with the why and end with the what. – Stu Hamilton

An integrated database of data from 51,101 lakes in the northeast United States has been developed to assist with the problems arising from too many disperse and limited data sources. Three decades of data can now be discovered in its location and context (i.e. land use, geologic, climatic, and hydrologic settings). The database contains 150,000 measures of total phosphorus, 200,000 measures of chlorophyll, and 900,000 measures of Secchi depth. – Stu Hamilton